Method and apparatus for treating hydrocarbon oils for subsequent cracking



E. A. OCON METHOD AND APPARATUS FOR TREAIING HYDROCARBON OILS FORSUBSEQUENT CRACKING I/.z J

ATTORNEY.

Patented sept. 21, i937 UNITED STATES PATENT METHOD AND APPARATUS'FOR.TREATING HYDROCARBON OILS FOR SUBSEQUENT CRACKING 19 Claims.

This application is a continuationin part of my application led August3, 1935,`Serial No. 34,563.

The object of this invention is to provide a i novel method andapparatus to produce low boiling point products, suitable as motor fuel,by treating in a primary blending, Vaporizing and fractionating tower,with the aid of highly heated cracked hydrocarbon-products and steampassed into said tower, one or a plurality of streams of hydrocarbonmaterials .ofhighboilingpoint which may be preheated, such as crude oil,topped crude oil, liquefied coal, shale oil and allied hydrocarbons, toform from the vaporized and unvaporized hydrocarbons in said tower, twostreams of puri.- ed substantially uncracked hydrocarbon fractions, eachof different composition and characteristics and being adapted forsubsequent cracking, the vaporized uncracked fractions of the chargingstock higher boiling than gasolineblend- `ed with the crackedhydrocarbon vapors higher boiling than gasoline of the highly heatedhydrocarbon products are. condensed, forming one stream, and theunvaporiz'ed portion of the uncracked charging stock mixed withentrained liquid of the cracked products forming the second stream, eachstream being led toaseparatecracking zone and subjected preferably todifferent racking reactions under conditions of temperature and pressuremost ecient tothecompositivon and characteristics of each stream formaximum conversion into low boiling point products, with the minimumformation of gas and almost complete absence of coke formation.

Another important object of. my invention is to provide a compositemethod for producing a novel sulfur treated synthetic hydrocarbonrecycling stock consisting of a. mixture of heavy fractions of differentcomposition and characteristics, namely condensed heavy uncrackedfractions from the substantially vaporizedinitial charging stock,condensed heavy fractions from the hydrocarbons heated under lowpressure to a mild cracking temperatureof about 850 F., and condensedheavy fractions from the hydrocarbons heated in a separate heating zone,u nder substantially higher pressure, to a higher cracking temperature.of about 1050 F. as hereinafter described. The invention furtherprovides a method in- .which the heavy residue, including tarry andsolid materials, is dropped from a zone in'the separationt'owermaintained in a. highly heated condition,- preferably gabove '750 acooling material being continuously Ipassed into contact with said heavyresiduesas 'they drop to the base of said heated zone for the reductionof temperature therein to avoid the formation of carbon.

The invention will be described with reference to the accompanyingdrawing in which I indiycates a pipe through which charging stock ispassed to the preheaters 2 and 3 and thence discharged below themidsection of primary frac- Ytionating tower d. Into the fractionatingtower l is discharged through pipe 5 controlled byvvalve 6' a suitablequantity of highly heated vapors which may be steam, and ammonia canalso be carried by the steam, if desired, and into tower li may also beinjected highly heated cracked hydrocarbon vapors passed into the towerthrough pipe l controlled by valve pipe l leading from thedischarge`endof a cracking coil indicated at 9 and disposed `within theconvection and "radiant lsections of a furnace lll, the convectionsection being separated from the radiant section lll by a wall indicatedby dotted lines l2.y Y

By the preheaters 2 and 3 or byv any other suitable means the chargingstock may be raised to a temperature of 50o-700 F. so that when the nowof charging stock contacts with the highly heated vapors the unvaporizedportion is raised in temperature and theI greater portion of its lowerboiling point fractions are released as vapor without cracking althoughthey may reach an incipient cracking^ temperature. therefore rises intower El. and meets a cooling material injectedthrough pipe it from thestraight run or light fraction tank It from which liquid may bewithdrawn by a pump l5. In this manner the straight run gasoline and anycracked gasoline resulting from condensation of theheavy fractions ofthe products injected through pipes l and 'l will be carried to the tankit via pipe i6 and condenser Il from the top of the tower 4 and repassedby pump l5 to the interior of the' tower for the purpose stated. Theheavy fractions that are condensed by the said cooling material arecollected in a pan da: being then passed through pipe I8 by pump I 8a:part to a blending, chamber 2U and part to the ,upper section ofseparating tower 30. That portion of the charging stock which isunvaporized in tower l will fall to the base thereof and will bewithdrawn through pipe 2l by pump 22 and passed to a second crackingcoil 23. Sulfur absorbent material such as triethanolamine,ethylenediamine, sodium plumbite, lead acetate and the like, one or amixture of two or more, preferably mixed with materials such as The`vapor alcohol, ether, water and gasoline or other suitable material,may be contained in a tank 2`4 and passed into tower 4 below the pan 4a:by means of a pump 24m to lower the sulfur content of the oil. Tower 4has at the base thereof a valve controlled drain pipe 25 to dischargesludge. The unvaporized portion of the charging stock is then cracked inthe lower temperature coil 23 of the furnace and is heated to atemperature, say from G-900 F. and is discharged into blending chamber20 simultaneously with vthe products cracked in the coil 9 of higherheat. I

Coil 9 receives via pipe 26 and branch pipe 21 controlled by pump 28 thepurilied composite heavy condensate of the second fractionating tower 29and consisting of the heavy cracked lfractions higher boiling thangasoline range obtained from coil 23, 4and the heavy condensate higherboilingthan gasoline range of the intermediate uncracked fractionsdelivered to blending chamber 20 from pan 4m, and blended with thecracked products of the two coils. The composite condensate passedthrough coil 9 is heated to a lcracking temperature of say, 1000-1100 F.and the blended productsvfrom both coils pass from blending chamber 20to a separation tower 30 and meeting the uncracked condensate from pan4x of the primary fractionating tower 4. The blending chamber willdischarge directly into a pan indicated at 30a: in which zone highturbulency is formed, and a temperature of 70D-800 F., more or less, ismaintained. As the pan lls to its top, the fuel oil constituent, tarrymaterial and carbon will overflow, as indicated by the arrows, and willthen drop to the base of the separation tower. The vapors rise and meeta reiiux consisting of part of the intermediate uncracked fractions fromthe primary fractionating tower 4 passing through pipe I8 controlled byvalves I9, |916, and a portion of the unvaporized oil of the primary.fractionating tower 4 passing from pipe 2I through a branch pipe 34discharging into the tower near the top thereof and into the towerIthrough branch pipe 3Icc, if the' latter is desired. Ordinarily, pipe 3Imay be eliminated.

Water or saturated steam and ammonia may be passed into tower 30 bymeans of valve control pipe 32. To cool the bottom of tower 30 aconstant level of fuel oil may be maintained therein, as by constantlywithdrawing the fuel oil through valve control pipe 33 by pump 34,cooling said fuel, returning the required proportion to tower 30 byvalve control pipe'35 and passing the balance not needed to maintain thelevel to a cooler 36 via pipe 31 and thence to storage. 'I'he withdrawalmember in tower -30 for the fuel oil pass'- ingto pipe 33 may consist ofa perforated tube 38. 'I'he dotted lines at 39 indicate appropriatelevels of fuel oil maintained in tower 30. At the base of tower 30 is avalve control draw-off pipe 25x for withdrawal of carbon and sludge fromtime to time, as required.

The lighter fractions pass from tower 30, preferably through catalyticmaterial indicated at 49, and thence to secondary fractionating tower29, this passage being through pipe 4-I.

As a regulator for the temperature of the vapors in fractionating tower29, steam maybe infrom pipe 27 into branch pipe 43, the hot vaporsexchanging heat to the incoming charging stock and thence passing intotower 29 through valve control pipe 44. Gasoline reflux may be passedinto the top of tower 29 through valve control pipe 45 from tank 46through the action of pump 4'I.` The tank 46 receives gasoline-typefractions from condenser 48 receiving gasoline vapors from pipe 49communicating with the interior of tower 29 at the top thereof and thehot vapors may exchange heat at heat exchange 2, transferring the sameto the charging stock passing through pipe I.

When it is desired to re-form the gasoline comprising the straight runand cracked gasoline fractions separated in fractionating tower 4, pumpI5 may be employed to pass such mixed gasoline through pipe 50 to pipe26, where the gasoline will meet the heavy condensate of secondaryfractionating tower 29 and the gasoline will be re-formed during thecracking of said condensate within coil 9.

As an example of operation of the process, into the primaryfractionating tower there is passed a regulated stream of uncrackedhydrocarbon such as crude oil or topped crude heated, for example, to700 F. and thereby substantially vaporized and raised in temperaturetherein by means of a blast of highly heated previously crackedhydrocarbon products admixed with water vapor passed into said tower,and having a temperature above 800 F., preferably 1000-1100 F., whichserve a three-fold purpose; first, reduce the Viscosity of the crudecharging stock; second, increase the de-4 lease therefrom the greatestportion of lower boiling point fractions without active cracking; third,increase the anti-knock value of the straight run gasoline separated bycooling from the vaporized heavy fractions of the charging stock byblending it with the cracked gasoline of the blast of highly heatedvcracked products, and then condensing said gasoline blend, 'separatelycondensingwithin said primary tower the heavy uncracked fractions andrevaporizing and mixing the same for mutual condensation with thecracked products resulting from heating, under a pressure rang'ebetween5 and 25 atmospheres, the unvaporized fractions of the stock to a mildcracking temperature of from 800 to 900 F., separately cracking, under apressure range between I5 and 60 atmospheres, said mixture of condenseduncracked and cracked fractions condensed in the second fractionatingtower, lblending the resulting products of the two cracking zones,separating the residue and subjecting the blended vapors tofractionation and condensation.

As another qexample of the process, into the primary fractionating tower4 there is passed a regulated stream of uncracked charging stocksuch ascrude or topped crude oil which may be preheated, and in the tower thepreheated charging Istock is raised in temperature by means of aregucreasing the degree of vaporization of the un-v cracked stock. lThisenables release therefrom of the greatest portion of the less volatileconstituents'of the charging stock, the thus released straight runAgasoline fractions joining the cracked gasoline from the blast ofcracked products. The vapors released above gasoline range areseparated, by cooling, from the mixed gasoline fractions and condensed,and separately condensing the said gasoline fractions. The unvaporizedfractions of the charging stock and entrained liquid of the blast ofcracked products are collected at the lower end of the primary tower 4and are carried to the cracking coil 23 receiving the lower temperatureand therein heated undera pressure range of between .5 and25atmospheresto a cracking temperature of approximately 850 F.

The resultingcracked products are blended with the uncracked heavycondensed fractions passed from the pan 4x to the blending chamber 29and separating tower 30. 'I'he mixture of cracked and uncracked heavyfractions above gasoline range collected in the secondary fractionating`tower 29 are separately heated in a coil receiving the highertemperature, to wit, member 9, to a cracking temperature ofapproximately 1050 F., under `pressure range between 15 and 60atmospheres, and the resulting products are'in turn 20 mixed in theblending chamber with the cracked 30 approximately at 1050 F., heavyfractions from the products cracked at 850 F., approximately, and heavyuncracked fractions from the heavy uncracked condensate from pan, 4x)are condensed and dropped to the base of tower 29 to 35 form acontinuous stream of recycling stock for passage through pipe 21 andbranch pipe 26 to said coil 9.

Sulfur reagent materials may be passed into the blending chamber 20through valve' control pipe 5I from any suitable source. pass intosuperheater 52 through pipe 52a: and part led to the coil 23 via valvecontrol pipe 53, an-d part of the steamfled to coil 9 via valve controlpipe 54.

Instruments such as thermowells, temperature controllers and recorders,etc., are not indicated or mentioned, but it is to be understood thatthey will be used as required, as is well known in the art.

It will be noted that in passing the heavy residues from` the base oftower 30 and thence back thereto in order that both cooling and aconstant level may be obtained, cooling may be veffected by passing thesaid heavy condensate through a heat exchange member 33a: with whichpipe 33 will communicate. In that case, Water and ammonia will enterpipe 32 and the water may be raised up to saturated steam degree by theheat exchange member for discharge into the separating tower 30. l

Although the herebefore described method is preferred, the system ofoperation may vary considerably as there are characteristics instructure and apparatus which make myinvention one of broad application,and it is to be understood that modification and changes may be madeprovided they do not depart from the scope of the invention of thefollowing claims covering the invention.

Having described my invention, what I claim and desire to secure byLetters-Patent, is as follOWS f Steam mayvaporization in a primaryfractionating zone through the aid of highly heated vapors from aheating zone passed into contact therewith, separating and condensing insaid zone the uncracked virgin gas oil fractions of said uncrackedcharging stock from the gasoline range fractions, withdrawing saidgasoline fractions from the fractionating zone, withdrawing theunvaporized thus treated heavy fractions of the charging stock from thezone and heating the same under superatmospheric pressure to a crackingtemperature of from 800 to 900 F., approximately, for a period suicientto produce substantial cracking, discharging the cracked products into ablending and separating zone,separating thereby the residue and tarrymaterial, leading the uncracked virgin gas oil of the charging stock tothe blending and separating zone and vaporizng it by mixing with thecracked vapors therein, passing the cracked and uncracked mixedhydrocarbon vapors into a secondary fractionating zone, separating andwithdrawing from said secondary fractionating zone the gasoline-rangefractions and condensing therein the fractions boiling at temperaturesabove the gasoline range,

and comprises gas oil fractions of the charging Vstock and the crackedheavy fractions of the crackedyapors, cracking said mixed condensedfractions under a higher cracking temperature than applied in thefirst-named cracking operation of the unvaporized charging stock andblend- -ing the resulting cracked products in said blending andseparating zone.

2. A process for forming'a synthetic hydrocarbon product comprising amixture of anuncracked vapor condensate boiling at temperatures abovethe' gasoline boiling point range ofan uncracked hydrocarbon chargingstock, and a heavy cracked condensate of a cracked stock for theproduction of low boiling point products of motor fuel type whichcomprises passing an initial uncracked charging stock heated undersuperatmospheric pressure to a temperature below cracking into a primaryvaporizing and fractionating zone, under lower pressure, wherein thecharging `stock is substantially vaporized, condensing the vaporizedfractions by contact with a cooling fluid, withdrawing from thefractionating zone the unvaporized fractions of the said charging stock.and heating them admixed with steam in a cracking zone undersuperatmospheric pressure range between 5 to 25 atmospheres, to arelatively low cracking temperature of from 800 to 900 F., ap-

proximately, passing the uncracked condensed fractions from thevaporizing and fractionating zone into a blending and separating zonewherein said condensate is completely vaporized by mixing it with thehot cracked vapors discharged from the cracking zone into said blendingand separating zone and from which the residue and tarry material hasbeen separated in said zone,

lpassing the mixed cracked anduricracked vapors pto a secondfractionating zone, separating the from said second cracking zone intosaid blending and separating zone and blending the same with the crackedproducts of the first-named cracking zone, mixing the blended crackedvapors with the uncracked condensed fractions of the first-namedfractionating zone to obtain overhead products of gasoline range and thesynthetic recycling product.

3. A process for treating hydrocarbon oils which comprises thesubjection of an initial uncra'cked oil charging stock to substantialvaporization in a zone through the aid of highly heated vapors passedinto contact therewith, separating in said zone the uncracked virgin gasoil fractions of said charging stock from the gasoline range fractions,withdrawing said uncracked gasoline fractions from the zone and forminga condensate thereof, subjecting ,said virgin gas oil fractions tovaporization obtained by the sensible heat of cracked hydrocarbon vaporscontacting therewith in a separating zone, passing the unvaporizedportion of the charging stock from the rst zone to a heating Zone andsubjecting the same to a cracking temperature of from about 800 to 900F., approximately, for a time sufficient to substantially crack the sameand discharging the cracked products into said separating zone, leadingthe mixed treated vapors from said separating zone and fractionating thesame to obtain a 'recycle condensate comprising uncracked heavyfractions higher boiling than gasoline of the vaporized virgin gas oiland heavy fractions higher boiling than gasoline of said crackedproducts, subjecting said recycled condensate simultaneously with thesaid uncracked gasoline range fractions condensate to a crackingtemperature of 900-1100 F., approximately, for a time sufllcient tosubstantially crack said condensate and reform said uncracked gasolinerange fractions, and discharging said cracked and reformed products intothe separating zone.

4. A process for forming hydrocarbons of the motor fuel type, whichcomprises, subjecting an initial hydrocarbon charging stock containingconstituents of higher boiling point than gasoline constituents tosubstantial vaporization without substantial cracking in a "preliminaryzone with the aid of a stripping action by highly heated vaporscontacted with the charging stock, separating vapors from theunvaporized charging stock, fractionating the separated vapors to form acondensate of higher boiling range than that of gasoline, deliveringliquid residual products into a second zone for separation of vaporsform liquids, withdrawing the unvaporized portion of 'the charging stockand subjecting same to heat under conditions of temperature andpressure,

and for a time sufficient to effect substantial cracking thereof to formmotor fuel hydrocarbons, passing the cracked products into the secondzone, simultaneously passing into said second zone a condensate ofhigher boiling range than that of gasoline fractionated out of thevapors separated in the preliminary zone, passing vapors from saidsecond zone to a second fractionating zone to condense out a fraction ofhigher boiling range than that of gasoline, subjecting said fraction tocracking conditions in a second cracking Zonato produce low boilingpoint hydrocarbon vapors, passing vapors from said second cracking zoneinto the preliminary zone to act as highly heated vapors for thestripping action.

5. A process in accordance with claim 4, in which cracked liquidresiduals sent to said second zone form apool in an intermediate sectionof the second zone, and the cracked vapor and liquid residual productsare injected into this pool.

6. A process in accordance with claim 4, in which liquids sent to thesecond zone form a pool in an intermediate section of said zone, theliquids being at a temperature at least equal to an incipient crackingtemperature and injecting heated gaseous material to contact with theliquids in order to secure a high degree of vaporization. j

7. A process forcracking and converting high boiling liquid hydrocarbonmaterials to form lower boiling hydrocarbon products of the motor fueltype which comprises, heating the hydrocarbon materials under crackingconditions in a heating zone to form liquid and Vapor products,maintaining a pool of liquid products in an intermediate section of aseparation zone at a high temperature to vaporize a portion of saidliquid products in such a manner that residual portions of the liquidproducts in the pool are forced to separate and flow downwardlycountercurrent to heated steam and ammonia vapors injected into theseparation'zone below the pool so as to have a stripping action on theresidual portions of said pool flowing downwardly, injecting into saidpool,highly heated cracked products from said heating zone, removinggaseous and vaporized materials from the separation zone, cooling thestripped portions to form a second pool below the first named pool andremoving residual portions from said second pool.

8. A process for forming hydrocarbon products of the motor fuel type,which comprises subjecting a preheated uncracked charging stock tosubstantial vaporization in a primary zone with the aid of highly heatedhydrocarbon products of cracking containing fractions of boiling rangeof naphtha passed into contact with and flowing counter-current to theunvaporized fractions 'of the' charging stock to produce a solvent and astripping action which substantially increases the amount of vapors,separating from said Vapors in said primary zone a thus formedsubstantially uncracked intermediate fractional condensate higherboiling than naphtha, withdrawing unvaporized charging stock from saidprimary zone, subjecting the same in a heating zone to a pressure, attemperature and for a time suiiicient to produce substantial cracking,delivering cracked products from said heating zone to a separation zone,passing the intermediate condensate from the primary zone to saidseparation zone to be revaporized by contact therein with cracked vaporproducts of said heating zone and of a second zone .hereafter described,passing mixed vapors from the separation zone to a fractionating zone toobtain a composite recycle condensate higher boiling than gasoline andcomprising a portion of the revaporized intermediate condensate andcracked products, cracking said composite condensate under higherpressure and temperature than that applied to the unvaporized chargingstock, and mixing the resulting cracked vapor products in saidseparation zone with the cracked vapor products of' the first namedheating zone and said revaporized intermediate substantially uncrackedcondensate above described.

9. A process for forming hydrocarbon products of motor fuel type inwhich a preheated initial hydrocarbon charging stock is subjected to asolvent action and substantial vaporization in a primary zone throughthe aid of highly heated vapors from a heating zone passed into contacttherewith and containing gasoline and naphtha,

simultaneously the unvaporized portion is suby ing zone underfsuperatmospheric pressure to a cracking temperature for a period oftimepsufcient to produce 'substantial cracking, delivering .the crackedvapor and liquid products to aseparating zone, injecting into the hotcracked vapor products in said separating zone for its revaporizationsaid intermediate fractional condensate from the primary zone,Ifractionating the vapors in a secondary fractionating Zone to separateout condensed fractions higher boiling than gasoline,

passing said condensed fractions from said second fractionating zone toa second heating zone in which said condensed fractions are crackedunder superatmospheric pressure, mixing the cracked vapor products afterseparation from liquid, 4from said second heating Zone with the crackedvapor products from said first mentioned heating zone and theintermediate fractional condensate withdrawn from the primary zone toobtain overhead products Aof ,gasoline boiling point range and heavierproducts. I

10; A process for cracking hydrocarbons to .produce motor fuels, whichcomprises subjecting a hydrocarbon charging stock to vaporization in aprimary zone to form vapors and residual oils with a minimum ofcracking, subjecting the vapors to fractionation to separate out afraction ofhigher boiling range than naphtha, passing from the primaryzone residual oils substantially free from'tarry bottoms to a heattreatment zone wherein said residual oilsl are subjected to crackingconditions toL convert hydrocarbons into lower boiling pointhydrocarbons, passing the resulting hot products from the heat treatmentzone to a separation zone for separating vapors from liquids, vaporizingin said 'separation zone a petroleum fraction higher boiling thangasoline comprising uncracked constituents, passing thus formed vapormixture from said separation zone to a fractionating zone to fractionateout a recycle condensate containing cracked anduncracked constituentshigher boiling than gasoline, and passing'the recycle condensate to asecond heat treatment zone for converting constituents in said recyclecondensate 'under cracking conditions, in which'hydrocarbon products ofboiling point range lower than gas oil and comprising fractions withinthe kerosene and heavy naphtha boiling point range are reformed byheating said products at a pressure not exceeding 60 atmospheres and notless than 15 atmospheres to a temperature above 1000 F., jointly withthe recycle-condensate, maintaining the products in said temperature andpressure conditionsfor a time sufficient to split constituents of saidrecycle condensate, including gasoline constituents, and reforming saidkerosene and heavy,naphtha boiling point range fractions and condensingand collecting a motor fuel product.

11. A process for cracking mineral oils to produce gasoline, whichcomprises subjecting to vaporization under expansion without substantialcracking an initial preheated raw mineral oil to form vapors andresidual oilsin a primary zonfinjecting into said primary Zone adesulfurizing agent to absorb sulphurous impurities from the raw mineraloil, passing a portion of the unvaporized raw oil of reduced sulfurcontent from the primary zone to a heating zone to be heated underconversion conditions suiiicient to cause formation of gasoline,separating vapors comprising gasoline from liquid products of theconversion, fractionating the vapors of the conversion to form acondensate of higher boiling range than gasoline, subjecting saidcondensate in a second heating Zone 'to more severe conversion 15conditions than imposed upon the unvaporized oil in said rst mentionedheating Zone, and passing productsy in heated condition from said secondheating zone to said primary zone to aid in the vaporization of theinitial raw oil.

12. A process in accordance with claim 8, in which vapor products fromthe separating zone including the fractions higher boiling than gasolineare subjected torening to remove sulphurous and other tar formingsubstances prior to fractionating the composite recycle condensate andcracking same.

13. A process for the conversion of hydrocarbon oils into refinedgasoline motor fuels, which comprises heating the hydrocarbon oils in acracking zone for a .time to form gasoline and under cracking conditionsof temperature and pressure, passing products from the cracking zone toa separation zone maintained at temper.-

atures of about 700 to 800 F. for separating 35 vapor products fromliquid products, admixing with the products at a lower pressure thanthat'. of the cracking zone and before entering the separation zone an.absorbent desulfurizing agent volatile at the said temperatures torefine the products, separating oil vapors thus refined from the thustreated products, further refining the separated vapors t6A remove fromthem undesirable sulphurou's and'tarry substances by ldirectly lpassingthe separated vapors through a catalytic contact mass andsending thevapors refined by said contact mass to afractionating ,zone to separateout a refined condensate higher boiling than gasoline for further heattreatment under cracking conditions and product.

14. A process in accordance with claim 13, in which hydrogenating gasesare mixed with the refined condensate, further heated under crackingconditions and at a pressure not exceeding 60 atmospheres and condensingand collecting a motor fuel product.

a refined overhead gasoline 15.` A process in accordance with claim 13,i

,which comprises reforming uncracked hydrof products, a furnace dividedinto radiant and convection sections, heating means in the radiantsection, separate cracking coils disposed primarily within theconvection section and having their outlets in the convection section ofthe furnace, one of said coils largely being in a radiant section andrelatively nearer the heating means than the second coil and comprisinga plurality of tubes at the highest section of the convection sectioncommunicating with a bank of tubes in the radiant section adjacent awall which divides it from the convection section, the latter tubescommunicating witha bank of tubes'in the radiant section opposite saiddivision wall, the latter tubes communicating with -a roof bank of tubesin the radiant section, and the roof bank of tubes communicating with amain tube section disposed intermediate the rst named tubes in theconvection section nearest the heating means and the tubes of the secondcracking coil, the tubes of the second cracking coil comprising aplurality of tubes at a roof bank in the convection section and thencecommunicating with a main tube section disposed between the outletsection of the first named cracking coil and the said outlet section ofthe second named cracking coil, a blending chamber receiving the crackedproducts from both coils, a vapor separating tower receiving the crackedproducts, means within the vapor separating tower for maintaining a poolof liquid in the intermediate section of said tower into whichC thecracked products are discharged, means for maintaining a pool of liquidat the bottom of said tower receiving heavy and tarry residues notvaporized in said intermediate pool, a fractionating tower receiving thecracked vapors of the vapor separating tower by means of a ow connectionintermediate the top of said vapor separating tower and the lowersection of said fractionating tower, means for injecting cooling uidinto said fractionating tower, a ilow connection between the botto-m ofsaid last named tower and inletof the first named cracking coil, aprimary vaporizing and fractionating tower receiving a charging stock,means within the last named tower for collecting unvaporized liquid atthe bottom and'vapor condensate in an "intermediate section of said lastnamed tower, a flow connection intermediate the outlet of the rst namedcracking coil and the bottom of said primary vaporizing andfractionating tower for causing a flow of highly heated products to saidtower to aid the vaporization of said charging stock, means forinjecting said vapor condensate into said blending chamber' andseparating tower, means for injecting cooling fluid into the uppersection and lower section of said separating tower, means for injectingcooling fluid into the upper section of said primary vaporizing andfractionating tower, means for injecting sulphur removal agents intosaid primary vaporizing and fractionating tower, a flow connectionbetween the bottom of said last named tower and the inlet of said secondnamed cracking coil for conveying thereto the unvaporized chargingstock, a flow connection between the top of said primary vaporizing andfractionating tower and a condensing means for condensing gasolinevapors, a flow connection between said condensing means and a separatingtank, .a ow connection between said tank and said first named crackingcoil, a flow connection between the top of said rst named fractionatingtower and condensing means for condensing therein gasoline vapors, meansfor injecting steam into the bottom of said primary vaporizing andfractionating tower and into the bottom of the rst named fractionatingtower, and means for injecting a solution of water and ammonia through aheat absorbent means into the bottom of the separating tower for arefining and stripping action.

18. A process in accordance with claim 11, in which the sulfur treatedvapor mixture comprising vapors of the initial rawoil and vapors of theheated products passed to the primary zone to aid in the vaporization ofsaid raw oil is con- V'densed, revaporizing'the condensate of reducedsulfur content in a zone distinct from the zone in which the vapormixture was condensed, and subjecting the vapor products of therevaporization to fractionation jointly with (the vapor products of thecracking from the rst named heating zo-ne.

19. A process in accordance with claim 11, in which the vapor mixturecomprising the vapors of the initial rawoil and vapors of the heatedproducts from the second heating zone passed into the primary zone arefractionated to obtain overhead products of boiling point range lowerthan gas oil, condensing in said primary zone the heavy fractions ofboiling point ranget of gas oil, revaporizing in a zone distinct fromsaid primary zone said heavy fractions comprising un-A cracked gas oilfractions of the initial raw oil and gas oil fractions of the heatedproducts from the second heating zone, and fractionating the vaporproducts of the revaporization jointly with the vapor products of thecracking from the first named heating zone.

ERNEST A. OCON.

